Tardive dyskinesia (TD) has been explained as a relative excess of dopamine (DA) transmission in its reciprocal balance with acetylcholine (ACh) transmission in the basal ganglia. A treatment strategy would be to compensate for this relative DA excess by increasing cerebral ACh tone, thereby suppressing the abnormal movements of TD. Orally administered choline has been shown to elevate blood and brain choline levels and brain ACh levels in rats and to increase blood and CSF choline levels in humans. Moreover, choline administration has suppressed abnormal movements in some patients with TD. Lecithin is the natural dietary source of choline and has also been shown to increase blood choline levels and to supress TD signs without the side effects of choline. In this study we propose to treat 50 TD patients with lecithin in a double-blind, placebo-controlled, crossover fashion. Intravenous physostigmine would be administered prior to the lecithin trial to assess its potential predictive value for lecithin response. Blood choline levels will be assayed for correlation with clinical response.